Oriented foamed polyolefin extrudates and the production and dyeing of the same



Oct. 26, 1965 A. BOTTOMLEY 3,214,234

ORIENTED FOAMED POLYOLEFIN EXTRUDATES AND THE PRODUCTION AND DYEING OF THE SAME Flled May 21, 1963 INVENTOR. ANTHONY BOTTOMLEY A T TORNE VS United States Patent 3,214,234 ORIENTED FOAMED POLYOLEFIN EXTRUDATES SSIZETHE PRODUCTEON AND DYEING OF THE Anthony Bottomley, Sharon, Mass., assignor to Phillips Petroleum Company, a corporation of Delaware Filed May 21, 1963, Ser. No. 283,950 23 Claims. (Cl. 855) This application is a continuation-in-part of application Serial No. 45,716, filed July 27, 1960, now abandoned.

This invention relates to plastic filaments and to a process for their manufacture.

The production of polymer, resin, or plastic filaments and the weaving of these filaments into fabrics for various uses such as in lawn and porch chair upholstery, seat covers for automobiles, etc., is of ascending significance in the plastics industry. This invention is concerned with new filaments of improved characteristics for such use and to a process for producing same.

Accordingly, it is an object of the invention to provide novel and improved filaments of plastic or polymer material which weave into improved fabrics. Another object is to provide a process for preparing these novel filaments. A further object is to provide novel plastic or polymer filaments of higher bulk to weight ratio than presently available filaments. It is also an object of the invention to provide a plastic or polymer filament of cellular structure which has improved dyeing properties. Other objects will become apparent upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises extruding a molten mixture of a normally solid plastic, resin, or polymer thru a small orifice and a foaming agent which is gaseous at the temperature of the mixture during extrusion so as to form a foamed filament and thereafter drawing the filament so as to orient same. The resulting foamed filament has substantially increased bulk to weight ratio, such as at least 1 /2 to 3 or 4 times that of the unfoamed filament, preferably, at least two-fold, so that fabrics woven from these filaments have substantially the same appearance as those woven from unfoamed filaments, yet they have not more than half the weight of the fabrics made from the unfoamed filaments. In addition, the cellular structure of the filaments makes it possible to dye them to a two-tone shade for novelty fabrics which is not possible with unfoamed filaments. Moreover, the dye permeates the entire filament or fiber so that the coloring elfect is superior in appearance to surface coloring and it does not disappear with wear.

The drawing of the foamed filaments is essential to restore the smooth external surface of the filament, since the undrawn foamed filament is extremely rough, due, no doubt, to the outwardly distended orifices left by the escaping foaming agent. By drawing the filament in a length ratio in the range of 4:1 to 1021, the external surface of the filament is made apparently substantially smooth.

The process of the invention is applicable to substantially all of the normally solid polymers, resins, and plastics, including thermosetting resins, polystyrene, polyolefins, and particularly, polyethylene. Polymers of aliphatic mono-l-olefins such as ethylene, propylene, butene- 1, hexene1, octene-l, and the like, make excellent filaments for weaving into fabrics when prepared in accordance with the invention. Polymers of aliphatic mono-1- olefins having a maximum of 8 carbon atoms per molecule and no branching nearer the double bond than the 4-position provide foamed and drawn filaments having particularly desirable properties. Homopolymers and copolyrners, as well as mixtures of homopolymers and copoly- 3,214,234 Patented Oct. 26, 1965 mers are suitable materials for the filaments of the invention.

A preferred embodiment of the invention is directed to the use of foamed and drawn filaments of polyethylene which in an unfoamed state has a density in the range of 0.95 to 0.98 and a crystallinity of at least 70 percent and, perferably, at least percent at atmospheric temperatures such as at 70 F. It has been found that the foamed and drawn filaments of this type of polymer posses exceptional properties as compared to other polymers. While this type of polyethylene polymer constitutes a preferred embodiment of the invention in foamed and drawn filament form, conventional high pressure polyethylene of lower density and crystallinity, as well as other polymers of aliphatic mono-l-olefins and other plastics and resins are within the scope of the invention.

A preferred method of preparing polymers of aliphatic mono-l-olefins and, particularly, of ethylene, is described in detail in the US. patent of Hogan and Banks, 2,825,721, issued March 4, 1958. This particular method utilizes a chromium oxide catalyst, containing hexavalent chromium deposited on a support of silica, alumina, silicaalumina, zirconia, thoria, etc. In the method of this patent, olefins are polymerized in the presence of a hydrocarbon diluent, for example an acyclic, alicyclic, or aromatic compound which is inert and in which thepolymer is soluble. The reaction is carried out at a temperature between about F. and. about 450 F. and, usually, under a pressure sufiicient to maintain the reactant and diluent in the liquid state. The polymers produced by this method, particularly the polymers of ethylene, are characterized by having an unsaturation which is principally either trans-internal or terminal vinyl, depending on the particular process conditions employed. When low reaction temperatures in the range of about 150 F. to about 320 F., and a mobile catalyst are used for polymerization, the product polymer is predominately terminal vinyl in structure. When the polymerization is carried out at higher temperatures and in a fixed catalyst bed, the polymer has predominately trans-internal unsaturation. Polymers prepared by both methods are also characterized by their high densities and high percentage of crystallinity at ambient temperatures.

Other procedures which employ different catalyst may also be used for preparing olefin polymers. For example, suitable polymeric starting materials can 'be prepared in the presence of organometallic compounds, such as triethylaluminum plus titanium tetrachloride, mixtures of ethylaluminum halides with titanium tetrachloride, and the like. Another group of catalysts which can be used comprises a halide of a Group IV metal such as, for example, titanium tetrachloride, silicon tetrabromide, zirconium tetrachloride, tin tetrabromide, etc., with one or more free metals selected from the group consisting of sodium, potassium, lithium, rubidium, zinc, cadmium, and aluminum.

Various gaseous, liquid, and solid foaming agents are effective in the process of the invention. In general these agents comprise materials which are gaseous at the temperatures of the molten plastic or polymer at the extrusion die. Solid materials'which decompose at these temperatures and yield gaseous products or components which react with other ingredients present in the melt to produce gaseous products are applicable. Any inert gas which is nondeleterious to the polymer or plastic being extruded is feasible. Such gases include N steam, CO low boiling hydrocarbons (propane, butane, pentane), and freon. Liquids include water, ammonia, and hydrocarbons which vaporize at the extrusion temperatures as pressure outside of the die is released. Solid materials include p,p'-oxibis(benzenesulfonyl hydrazide) which is sold under the trade name of Celogen by Naugatuck Chemical, a division of the United States Rubber Company; diazoaminobenzene, dinitrosopentamethylenetetramine, 4-nitrobenzene sulfonic acid hydrazide, beta-naphthalene sulfonic acid hydarzide, diphenyl-4,4'-di(sulfonyl azide), and mixtures of materials such as sodium bicarbonate with a solid acid such as tartaric acid.

The amount of foaming agent to be used in the process is in the range of 0.01 to 50 weight percent of the polymer or plastic being extruded. Amounts in the range of 1 to weight percent are preferred.

The temperature employed at the extrusion die varies with the type of plastic or polymer being extruded, it being essential that the molten plastic be at a temperature which facilitates efficient extrusion. The extrusion temperatures of various plastics and polymers are well known in the art. Generally extrusion temperature will be in the range of about 250 to 600 F. and usually in the range of 350 to 550 F. Extrusion pressures will vary with the type of plastic or polymer and the foaming agent incorporated therein and will range from about atmospheric to as high as 700 or 800 p.s.i.g.

A more complete understanding of the invention may be had by reference to the accompanying drawing which is a flow illustrating a preferred embodiment of the process of the invention. An extrusion device 10 is provided with a hopper 12 for feeding polymer or plastic into the extruder in particulate solid form. The extruder is provided with a screw 14 which is power operated by means not shown attached to shaft 16. When utilizing a sold foaming agent, this agent is admixed with the particulate plastic and introduced to hopper 12. Liquid foamers may also be introduced in this manner. It is also feasible to introduce liquid and gaseous formers thru hollow shaft 16, providing passageway 18 which opens thru outlet 20 into the interior of the extruder and outside of the screw. A more detailed showing of an extruder screw of this type is shown in U.S. Patent 2,860,377.

The extruder 10 is provided with heating means (not shown) in the form of an electrical resistance coil surrounding the barrel of the extruder or a jacketed extruder barrel having inlet means at the extrusion end of the barrel and outlet means at the opposite end for circulating heat exchange material therethru. The temperature effected by the heat exchange is regulated so that the plastic or polymer is melted and is admixed with the foaming agent as it passes thru the barrel toward the extrusion end. A channel 22leads from the extrusion end of the barrel to the extrusion die 24. The extrusion temperature is measured at die 24 and is regulated by controlling the heat exchange in the extruder.

The molten plastic or polymer containing the foaming agent is extruded thru small orifices in die 24 to form foamed filaments 26 due to the escape of the foaming agent which is volatile at extrusion temperatures and readily escapes from the filament outside of the extrusion die. The foamed filaments are passed over roller 28 in cooling tank 30 which is provided with a suitable liquid coolant, such as water. The filaments are then passed over roller 32 and over rollers 34 and 36 in steam cabinet 38 which heat conditions the filaments for the drawing step. The drawing is effected in conventional manner applied to the drawing of unfoamed filaments by controlling the tension between rollers. The foamed and drawn filaments pass over roller 40 and onto individual storage rollers 42, 44, 46, etc.

When extruding monofilaments the diameter of the extrusion orifices will be in the range of about to 40 mills and when extruding filaments for multifilament yarn these orifices will be in the range of about 5 to 15 mills. The diameter of the filament can vary greatly and is not a part of the invention.

In order to illustrate the invention, the following specific examples are set forth. These examples are to be 4.- construed as illustrating the invention and not as unnecessarily limiting the same.

EXAMPLE I A blend of polyethylene and 2 percent Celogen AZ was extruded through extruder zones (1) 400 F., (2) 450 F., and (3) 350 F. and a 0.042 inch diameter to produce a foamed fiber of 37 mils diameter and 2925 denier. This fiber had a strength of 1.74 grams per denier and 11 percent elongation. Test data are shown in An unfoamed fiber of 37 mils diameter would be 6100 denier. This indicates over a 2 to 1 blowup of the foamed fiber.

EXAMPLE II High density polyethylene was blended with 2 weight percent Celogen foamer and extruded thru a die having orifices .042 inch in diameter at a temperature of 450 F. The foamed filament was rough, but it was drawn continuously at a 6 /z:1 ratio and the drawn filament appeared smooth. This sample was 37 mils in diameter and 2,925 denier. A 37 mil filament of the raw polyethylene (no foamer added) was 6100 denier. This indicates a 2:1 blowup of the foamed fiber. Tenacity tests gave the following results:

Denier Grams per Percent Denier Elongation The polyethylene used in the foregoing tests (both examples) had the following characteristcs:

Melt index 1.5

Density 0.960 Softening temperature, F 260 Crystalline freezing point, F. 252

Tensile strength, p.s.i 4400 Elongation, percent 20 Environmental stress cracking, hours 10 EXAMPLE III A melt of high density polyethylene containing 2 weight percent of Celogen AZ was extruded thru a 37 mil orifice into a filament or fiber. The resulting fiber was drawn at a ratio of 6 /2 to 1 and then quenched in a dye bath to ascertain its dyeing characteristics.

The filament accepted dye entirely throughout its structure by imbibing the dye bath. A transverse cross section of the dyed filament showed dye to be rather uniformly deposited or dispersed therein. Apparently, the pores of the foamed fiber extend to the surface thereof to facilitate complete dyeing to the center of the fiber.

The particular dye bath used in this example was Celanthrene brilliant blue FFS dispersed in water and the fiber or filament took on a two-toned blue effect, i.e., lighter and darker shades of blue, giving a two-tone appearance. This indicates the hydrophilic nature of the foamed filaments produced by the process of the invention.

The porosity of the foamed filament was not visible to the naked eye and did not detract from the appearance of the filament, it having an apparently smooth surface. The characteristics of the filaments of the invention render same ideally suited for weaving fabrics for seat covers, upholstery, and other applications where lightweight durable fibers are particularly desirable. The dyeing qualities of the fibers produced by the invention are outstanding. Because the color permeates the entire fiber, as contrasted with surface dyed fibers, wearing away of the surface of the fibers does not change the color thereof. The color is a permanent feature of the woven fabrics which no amount of Wear can change.

Dyes of the dispersed type which were developed for dyeing cellulose acetate are effective in dyeing the porous filaments of the invention. These dyes are insoluble in water but contain a dispersing agent which enables a very fine suspension to be formed in Water. Being more soluble in the polymer than the water they migrate from the water into the polymer. Normally, the depth of penetration is very small when applied to polyolefins, being 5.5 mils when exposed to the dye bath for thirty minutes. However, when applied to the porous filaments, the dye was accepted and dispersed completely throughout the filament in approximately one minute.

Any of the dyes utilized in the textile industry for dyeing artificial fibers may be applied to the instant filaments. Dispersed dyes which are effective include, in addition to Celantherene brilliant blue FFS C.I. 61,505, Celanthrene violet CB C.I. 61,605, Celanthrene red 3 EN C.I. 60,710, Celantherene fast pink 3B, Cl. 62,015, Acetamine scarlet B C.I. 11,110, etc. Any dyes absorbable into the pores of the porous filaments are applicable to dyeing these filaments. The numbers following the specifically mentioned dyes are the Color Index numbers given in the Color Index of The Society of Dyers and Colourists (England), 1956, vol. 4.

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

I claim:

1. A foamed and substantially longitudinally oriented strand of a polyolefin having substantially increased bulk to weight ratio compared with the unfoamed polyolefin, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polyolefin is molten and while said strand is being formed, the polyolefin being oriented after it has been foamed.

2. A foamed and substantially longitudinally oriented strand of a homopolymer or copolymer of ethylene or propylene having substantially increased bulk to weight ratio compared with the same unfoamed polymer, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while the polymer is molten and while said strand is being formed, the strand being oriented after it has been formed.

3. A foamed and substantially longitudinally oriented strand of a polymer of at least one aliphatic mono-1- olefin having a maximum of 8 carbon atoms per molecule and no branching nearer the double bond than the 4-position, said strand having a substantially increased bulk to weight ratio compared with the same unfoamed polymer, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polymer is molten and while said strand is being formed, the strand being oriented after it has been foamed.

4. A foamed and substantially longitudinally oriented strand of a polyolefin having substantially increased bulk to weight ratio compared with the same unfoamed polyolefin and longitudinally drawn to at least about 6 times the unoriented length of said polyolefin, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to saidstrand while said polyloefin is molten and while said strand is being formed.

5. A foamed and substantially longitudinally oriented strand of a polyolefin having substantially greater bulk to weight ratio than the same unfoamed polyolefin and having a denier at least in the 700s, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polyolefin is molten and while said strand is being formed, the polyolefin being oriented after it has been foamed.

6. A multifilamentous material of a plurality of foamed and substantially longitudinally oriented strands of a polyolefin having substantially increased bulk to Weight ratio compared with the same unfoamed polyolefin, said strands being foamed throughout their entire mass and said foamed characteristic being imparted to said strands while said polyolefin is molten and while said strands are being formed, the polyolefin being oriented after it has been foamed.

7. A multifilamentous material of a foamed and substantially longitudinally oriented polyolefin having substantially greater bulk to weight ratio than the unfoamed polyolefin, the individual filaments having :a denier at least in the 700s, said filaments being foamed throughout their entire mass and said foamed characteristic being imparted to said filaments while said polyolefin is molten and while said filaments are being formed, the filaments being oriented after the filaments have been formed.

8. A formed and substantially longitudinally oriented strand of a polyolefin having a bulk to weight ratio in the range of from appreciably greater to about 2 compared with the same unfoamed polyolefin, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polyolefin is molten and while said strand is being formed, the polyolefin being oriented after it has been foamed.

9. A foamed and substantially longitudinally oriented polyolefin strand having a bulk to weight ratio of at least about 1.5 times that of the unfoamed and drawn strand of the same polyolefin, and longitudinally drawn to a length in the range of 6 to 10 times its unoriented length, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polyolefin is molten and while said strand is being formed.

10. A dyed foamed and substantially longitudinally oriented strand of a solid resin comprising a polymer of at least one aliphatic mono-l-olefin having a maximum of 8 carbon atoms per molecule and no branching nearer the double bond than the 4-position, said strand being formed throughout its entire mass and said foamed characteristic being imparted to said strand while said resin is molten and while said strand is being formed, said strand being oriented after it has been formed.

11. A foamed and substantially longitudinally oriented polyolefin strand characterized by dye receptive cellular structure throughout its entire mass, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand while said polyolefin is molten and while said strand is being formed, said polyolefin being oriented after it has been foamed.

12. A foamed and substantially longitudinally oriented strand of a solid polymer of ethylene or propylene having a bulk to weight ratio of 1.5 to 4 times that of the unfoamed and drawn strand of the same polymer, said strand having an open porous structure and the capacity to imbibe a dye throughout its structure, said strand being foamed throughout its entire mass and said foamed characteristic being imparted to said strand While said polymer is molten and while said strand is being formed, the polymer being oriented after it has been foamed.

13. A foamed and substantially longitudinally oriented strand of a polyolefin having open porosity throughout its entire mass, said strand having been foamed throughout its entire mass and said foamed characteristic having been imparted to said strand while said polyolefin is molten and while said strand is being formed, the polyolefin being oriented after it has been foamed.

14. A fabric of foamed and substantially longitudinally oriented polyolefin filaments having substantially increased bulk to Weight ratio compared with the unfoamed polyolefin, said filaments being foamed throughout their entire mass and said foamed characteristic being imparted to said filaments while said polyolefin is molten and while said polyolefin is being extruded, the filaments being oriented after the filaments have been formed.

A foamed, substantially longitudinally oriented and elongated extrudate of a polyolefin having substantially increase-d bulk to weight ratio compared with the unfoamed polyolefin, said extrudate being foamed throughout its entire mass and said foamed characteristic being imparted while said polyolefin is molten and while it is being extruded, the polyolefin being oriented after it has been foamed.

16. A process for producing a foamed and substantially oriented extrudate of a polyolefin which comprises forming a molten mixture of said polyolefin and a foaming agent, adapted to foam said polyolefin during extrusion at the temperature and pressure conditions of the extrusion of said polyolefin, while maintaining the mixture under sufiicient pressure to prevent foaming, the proportion of foaming agent being such that the resulting foamed extrudate has a substantially increased bulk to weight ratio, forming an extrudate of said polyolefin by expression of said molten mixture through a die, foaming said extrudate during said extrusion and orienting said extrudate by subjecting the same to substantial drawing.

17. The process of claim 16 wherein said polyolefin is selected from homopolymers and copolymers of ethylene and homopolymers and copolymers of propylene.

18. A process for producing a foamed filament of at least one polyolefin which comprises forming a molten mixture of said polyolefin and a foaming agent selected from inert gases, volatile liquids and finely comminuted solids which form gaseous products at the temperature and pressure conditions at which said filament is formed while maintaining the mixture under sufiicient pressure to prevent foaming, the proportion of foaming agent being such that the resulting foamed filament has a substantially increased bulk to weight ratio, forming a filament from said mixture, foaming said filament while it is being formed, and substantially orienting said filament by drawing.

19. The process of claim 18 wherein said polyolefin is an aliphatic mono-l-olefin having a maximum of 8 carbon atoms per molecule and no branching nearer the double bond than the 4-position.

20. The process of claim 18 wherein said polyolefin is selected from homopolymers and copolymers of ethylene and homopolymers and copolymers of propylene.

21. The process of claim 18 wherein said polymer comprises essentially polyethylene having a density in the range of 0.94 to 0.98 and a crystallinity of at least percent at atmospheric temperatures.

22. The process of claim 18 wherein said polyolefin is selected from homopolymers and copolymers of ethylene and homopolymers and copolymers of propylene, and the extrudate has a denier of at least in the 700s.

23. The process of claim 18 wherein said polyolefin is selected from homopolymers and copolymers of ethylene and homopolymers and copolymers of propylene and said orienting is accomplished by drawing the foamed extrudate in a length ratio of from about 3:1 to about 10: 1.

References Cited by the Examiner UNITED STATES PATENTS 1,831,030 11/31 Picard 264-290 1,964,659 6/34 Brumberger 264-290 2,492,425 12/49 Hall et a1.

2,888,415 11/55 Jankens 264-54X 2,835,551 5/58 Kosuge.

2,862,284 12/58 Wiczer 28-82 2,905,648 9/59 Haas 26454 X 2,904,840 9/59 Hochreuter 260-25 2,948,048 10/60 Jankens 264-54 2,965,925 12/60 Dietzsch 264-209 2,999,296 9/61 Breen et a] 161-169 3,015,873 1/62 Dietzsch 264209 3,057,037 10/62 Carney et al 161-169 3,072,584 1/63 Karpovich 260-25 3,072,972 1/63 Yokose 260-25 X 3,102,323 9/63 Adams 260-40 3,118,161 1/64 Cramton 264-54 NORMAN G. TORCHIN, Primary Examiner.

EARL M. BERGERT, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 214 ,234 October 26 1965 Anthony Bottomley It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, Table I, first column, line 3 th 150 "Celogen" Z" read "Celogen" AZ column 5, line 28, for "61,605" read 61,105 column 8, after line 42, insert the following 3,121,130 2/64 Wiley et al.

Signed and sealed this 20th day of Se tember 1966.

5EAL) LttCSt:

RNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents 

15. A FOAMED, SUBSTANTIALLY LONGITUDINALLY ORIENTED AND ELONGATED EXTRUDATE OF A POLYOLEFIN HAVING SUBSTANTIALLY INCREASED BULK TO WEIGHT RATIO COMPARED WITH THE UNFOAMED POLYOLEFIN, SAID EXTRUDATE BEING FOAMED THROUGHOUT ITS ENTIRE MASS AND SAID FOAMED CHARACTERISTIC BEING IMPARTED WHILE SAID POLYOLEFIN IS MOLTEN AND WHILE IT IS BEING EXTRUDED, THE POLYOLEFIN BEING ORIENTED AFTER IT HAS BEEN FOAMED. 